[Mild cognitive impairment in Parkinson's disease].

Parkinson's disease (PD), a neurodegenerative disease, has been traditionally defined by its characteristic motor symptoms. Non-motor symptoms, including mood disorder, psychosis, sleep disturbance, autonomic dysfunction, and cognitive impairment, have being recently recognized as symptoms of PD. Cognitive impairment or dementia is one of the critical symptoms during the advanced stages of PD and is associated with increased disability and reduced quality of life of both patients and caregivers. The point prevalence of dementia in PD is about 30%, and its incidence rate in PD patients is 4-6 times higher than that in age-matched controls. The term mild cognitive impairment (MCI) has been adopted to describe the potential prodromal stage of dementia in PD, which has been gaining increasing attention. Several studies have reported the clinical features, epidemiology, biomarkers, and neuropathology of MCI in PD; however, neither the precise definitions nor the employed criteria were consistent across these studies. Recently, the Movement Disorder Society Task Force proposed new diagnostic criteria for MCI in PD to allow clinicians to identify PD patients with increased risk of dementia. Further studies are needed to validate the proposed criteria in daily clinical practice.